5V PS/2 Board Failure Causes

Interesting John! Any possibility of saving the boards with a simple capacitor replacement? I assume there is more damage. George

It appears that the usual casualty is some diodes in the middle of the sandwich, totally out of reach for replacement.  GGG says he's worked around that, but I don't think it's worth the trouble as a rule.  I figure I'd have to replace all the caps and fix whatever else got cooked to have any confidence in the board.  That looks pretty problematic to me.

I don't think it is bad caps.  Those caps are also on LocoSounds boards of the same vintage and they don't fail.  Replacing the cap rarely fixes the boards.  I think the diode failures or other component allows the + polarity to get on the negative of the cap and that causes the swelling/failure.

I have seen them when just an internal diode fails.  Replacing it gets it back, other times there is more wrong.

Audio amps usually are just that a bad amp.  Replacing it restores the board.   G

I have quite a few of these boards in my engines. Am I doomed here? Is failure just a matter of time?

I do.  I have a high success rate on repairing PS-2 3V boards.  The success rate for PS-2 5V is much lower, unless it is just the audio amp or some lighting feature problem.  I am 1 for 2 on PS-3, but the one win was on a PS-3 Diesel board.  My e-mail is in my profile.  G

I don't think so.  If your using them and they have been running fine, I think you will be ok.  The PS-2 5V went through a lot of revisions modifying components.  The ones that run seem to run fine, but there are early board sets that seem to fail with low hrs.  G

George,

What were you able to fix on a PS3?

Dave

Good catch John. I was aware of the bulging cap issue as we had to replace a number of PC motherboards and video cards in some of our older PCs. Worth a look to see if any of my 5V engines have that problem.

Pete

When failure occurs, what is the most common/cost effective fix?

For 5V boards, the typical fix is usually a replacement 3V board.  I've managed to fix two out of about 25 5V boards that were totally dead.  I have replaced a number of lighting transistors and one audio amp on them, those are parts you can get to.

I just toss the dead ones into a box in case I ever need a part.

Funny thing, the early boards were manufactured around the time of the great capacitor debacle.  While I know you reject the notion that this could be the issue, the fact is that when a capacitor shorts, it can take the diodes out pretty quickly.  I don't know for sure that's the issue, but I'd give it a decent chance for being the reason that some older 5V boards fail with so little runtime.

John,  Actually I have removed capacitors and measured them.  Swollen and still no short at the capacitor.  Additionally it is always the same capacitor that shorts.  Not the similar others.  I just don't think the data fits.  Additionally, if my memory is correct, that capacitor issue was with a specific manufacture and specific computers.  Not every product from that time frame.

I have dissected the boards and replaced various components and it goes deeper than that specific Cap.  Normally the high amp short is allowed to persist, clears itself to an open.   G

Heat FET that shorted the board.  G

George, This can't really be answered.  If it is a simple component, component level repair.  If you need a new board, there is the used 5V option, or going with the 3V board with new speaker and battery/harness.  For Premier or sentimental engines the 3V is worth the repair, you also get more sound file options typically.  G

GHD:  Not necessarily doomed.  I just replaced the board on a 2001 loco that hadn't failed, but intermittently would lose speed control:  it was stop or full speed.   I also replaced a pair of 2004's or 05's that had failed due to dead shorts. 

Get John & George in the same thread discussing the subjects they know best is like attending an MTH update seminar.

Thanks for sharing your knowledge with us.

John,

That is one grimm photo . A couple of those look just like the one from my dead switcher where one of the caps is a little suspicious looking on top. Great post though. I love "root cause" stuff like this. Also a very interesting read on the great capacitor plague. I'm sure the guy that stole the incomplete formula had a lot of questions to answer at his new company.

S

I think a lot of people have a few dead 5V boards around, they're easy to come by.

Scott, I guess you don't want to look in my box than....unfortunately you will see some PS-2 3V processors that were electrocuted with AC power onto the DC circuit.

But you will only see 2 PS-2 Power Supplies that I could not fix.  Hugh one is yours, of course that was the third resuscitation I think.  G

I have a couple of 3V boards that were too far gone to fix, but most have been revived and pressed back in service.

Question for grj and/or GGG:

For the problematic PS-2 sound amp and speed control chips, would it be possible to solder a chip socket on the PCB and simply plug 'n play new chips as needed?

Rod

I'm just curious here, but wondering what percentage of the 5V boards do you believe have failed to date. I suspect the total number of boards out there is confidential, but you gentlemen probably have a feel for this. I'm hoping that the number is small, like 5% or less. 

Hoping for a simple fix on the one I'm going to send you when I get around to packing it.

S

GHD< I hate to be the bad news bear, but out of 5, I've had 3 failures, one of which was an intermittent loss of speed adjustability (i.e., stop or full speed, cured by a reset) rather than total failure. 

No, These are smaller SMD packages.  Especially the audio amp.  G

Really could not say.  But I would agree that the number is smaller considering the volume out there.  What can be frustrating is relatively new engine with low hrs that fail.  Other well worn engine have no issues. 

It just is a consideration considering that they normally are not repairable.  G

I have a Premier MTH Bipolar that at 2 miles started making a terrible static sound. Everything on the engine works as it should and runs great on DCS. Is this the audio amp issue you spek of? If so, is it correctable or put a 3V board in. I have already replaced the speaker but it did not correct the issue. Thanks in advance for oyur help

Dave 

I was going to say speaker, but you already changed that.  It may be.  I would look at wire routing, make sure no issues with that, especially near the battery.  If none of that resolved the static, I would test board in the fixture and if static followed the board, I would recommend changing the audio amp.   G

When you're looking at the wiring routing, also make sure all the connections are secure and the contacts in the connectors are not loose.

My Rail King L-1 stopped on a switch, went dead, and then kicked my layouts circuit breakers.  I checked the trucks and pickup rollers for shorts but they are not the problem.  Could this be part of the cap issue that you guys are discussing?

Most probable cause is that a roller was contacting center rail and the same or the other roller an outside rail.

That may explain the original short, however, when I place the loco on a test track it still shorts out.

The PS-2 5V has a number of failure points that go beyond capacitors.  Circuit that operated at there design limits.  In one case over the limit and the software was written to limit the audio amp volume at start up to prevent overloading the 5V power supply. This was a pretty short live board (2000-2004) with numerous revisions and modifications to the board.  The PS-2 3V on the other hand has spanned the time (even those with the same potential capacitor time frame and only 2 revs to the processor board/power supply.

I think there is a lot more involved and if you look at enough 5V boards you will see major modifications and component changes on the board that go beyond obsolete parts.

Just my 2 pennies.  G

The defective capacitors were manufactured in the 2002-2003 timeframe, by 2004 they were pretty much out of the supply chain.

I'm not saying that all, or even a majority of the 5V board failures are related to these bad capacitors.  I am saying that it could well be one of a number of issues that surfaced to cause some of the failures.  Since I saw these capacitors in a lot of different devices at the time, I know the symptoms well.

If convenient to access the board-set, pull the 7-pin harness (typically red-red-blk-blk-gry-org-blu) connector from the smaller board.  This disconnects track voltage from the boards.  If you are "lucky" and the short persists, then it's likely a problem in the wiring or tether between the roller/wheels to the board - arguably easier to track-down and fix than a defective cap.

Of course if you can see a bulging capacitor on the board the 7-pin connects that's no so lucky.  Look for an expanded top/lid of the cap or perhaps leaking brownish electrolyte though as pointed out there are different or even no visual indications of failure.

Thanks everyone.  I disconnected the 7-pin harness and the short was alleviated.  So it must be in the board-set.  I could not find any visual sign of failure but as you say, sometimes that is the case.  I purchased the engine at York for $165 so I feel that replacing the board is not cost effective.  I will probably place the engine on ebay listed as "parts only".  Thanks again, guys.